Leukaemia is a cancer of the white blood cells; these cells are produced by the bone marrow. There are a number of different types of leukaemia.

Leukemias are divided into two main groups acute and chronic and then further divided by the type of white blood cell which is affected. Acute leukemias come on suddenly, often within days or weeks, progressing quickly and need to be treated urgently. Chronic leukemias develop more slowly often over many months or years.

There are four main types of leukaemia:

• chronic myeloid (CML)
• acute myeloid (AML)
• chronic lymphocytic (CLL)
• acute lymphoblastic (ALL)

Another type of leukaemia is the less common hairy cell leukaemia.

Each disease has its own characteristics and treatment.